High-conductivity high-transference number lithium metal battery gel electrolyte, preparation method thereof and lithium battery

Abstract

The invention relates to a high-conductivity high-transference number lithium metal battery gel electrolyte and a lithium battery, the gel electrolyte comprises gel and a lithium salt dissolved in the gel; wherein the gel is prepared by carrying out polymerization reaction on polymerizable ionic liquid, polymerizable zwitterionic monomers, an initiator and a cross-linking agent in an organic solvent. The positive electricity center in the ionic liquid on the main chain of the gel electrolyte and the positive electricity center in the bipolar ions jointly generate electrostatic interaction with anions in the electrolyte, migration of the anions is limited, a high lithium ion migration number is obtained, and therefore generation and growth of dendritic crystals are reduced; meanwhile, negative electricity centers at the tail ends of the bipolar ions promote dissociation of the lithium salt, high conductivity is obtained, and the electrochemical performance of the lithium ions is improved.

Description

Technical Field

[0001] The present invention relates to the field of electrolyte technology, in particular to the technology of using gel polymer electrolyte in lithium metal batteries, and specifically to a high-conductivity and high-migration number lithium metal battery gel electrolyte and a preparation method thereof, as well as a lithium battery. Background Art

[0002] In electrochemical energy storage technology, lithium metal batteries are widely used due to their low redox potential (-3.04 V relative to standard hydrogen electrode) and high theoretical specific capacity (3860 mAh g -1 ) has attracted widespread attention. However, in practical applications, the uneven deposition of lithium leads to a large number of dendrites on the surface of the lithium metal negative electrode. Lithium dendrites greatly affect the stability of the electrode and electrolyte surfaces, and the growth of lithium dendrites may even eventually puncture the diaphragm, causing the risk of battery short circuit and thermal runaway. In addition, the high reactivity between metallic lithium and the electrolyte will produce a large number of side reactions, reducing the cycle stability of lithium metal batteries.

[0003] A high lithium ion migration number can alleviate the concentration polarization phenomenon on the surface of the electrode and the electrolyte during the charge and discharge process, inhibit the formation of the "ion depletion layer" on the surface of the negative electrode, and thus protect the negative electrode and reduce dendrites. The current methods for increasing the lithium ion migration number include: using high-concentration lithium salts, single-ion conductors, etc. Among them, the single lithium ion conductor polymer electrolyte is to connect the anion to the main chain of the polymer in a covalent bond, so that only lithium ions move, and the lithium ion migration number is close to 1, which reduces the concentration polarization of lithium ions. However, due to the interaction between lithium ions and anion groups, the dissociation of lithium ions is reduced, resulting in a lower single-ion conductor polymer electrolyte, which affects the actual electrochemical performance of lithium-ion batteries. Summary of the invention

[0004] In view of the above problems, a high conductivity and high mobility number lithium metal battery gel electrolyte and a preparation method thereof and a lithium battery are provided to meet the application requirements of high mobility number and high conductivity gel electrolytes.

[0005] The specific technical solutions are as follows:

[0006] The first aspect of the present invention is to provide a high conductivity and high mobility lithium metal battery gel electrolyte, the gel electrolyte comprising a gel and a lithium salt dissolved in the gel;

[0007] The gel is prepared by polymerization reaction of polymerizable ionic liquid, polymerizable zwitterionic monomer, initiator and crosslinking agent in an organic solvent.

[0008] Specifically, the molar ratio of the ionic liquid to the zwitterionic monomer is 1:(0.5-2).

[0009] Specifically, the ionic liquid is one or more of 1-allyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-allyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-allyl-3-ethylimidazolium bis(trifluoromethanesulfonyl)imide, 1-allyl-3-butylimidazolium hexafluorophosphate, 1-allyl-3-butylimidazolium bis(trifluoromethanesulfonyl)imide, 1-allyl-3-methylimidazolium tetrafluoroborate, 1-vinyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-vinyl-3-methylimidazolium hexafluorophosphate, 1-vinyl-3-ethylimidazolium bis(trifluoromethanesulfonyl)imide, 1-vinyl-3-ethylimidazolium hexafluorophosphate, and 1-vinyl-3-ethylimidazolium tetrafluoroborate.

[0010] Specifically, the zwitterionic monomer is one or more of [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide, 2-methacryloyloxyethyl phosphorylcholine, and 1-propylsulfonic acid-3-vinyl imidazole inner salt.

[0011] Specifically, the lithium salt is one or more of lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium perchlorate, and lithium tetrafluoroborate.

[0012] Specifically, the initiator is an azo initiator or a peroxide initiator.

[0013] Specifically, the organic solvent is one or more of dimethyl carbonate, ethylene carbonate, propylene carbonate, diethyl carbonate, tetrahydrofuran, 1,3-dioxolane, diethyl carbonate / ethylene carbonate, ethylene glycol dimethyl ether / 1,3-dioxolane, and ionic liquid.

[0014] The second aspect of the present invention is to provide a method for preparing the above-mentioned high conductivity and high mobility lithium metal battery gel electrolyte, comprising:

[0015] Adding a polymerizable ionic liquid, a polymerizable zwitterionic monomer, a lithium salt, an initiator, and a crosslinking agent into an organic solvent, and stirring and mixing the mixture to form a mixed solution;

[0016] The mixed solution is dripped onto a polypropylene separator, and a high-conductivity and high-migration number lithium metal battery gel electrolyte is formed after encapsulation and thermal polymerization.

[0017] The third aspect of the present invention is to provide a lithium battery, wherein the electrolyte in the lithium battery is the above-mentioned high-conductivity and high-mobility number lithium metal battery gel electrolyte.

[0018] The beneficial effects of the above scheme are:

[0019] Compared with single-ion monomers, the ionic liquid monomers and zwitterionic monomers in the present invention have more selectivity, and the positive charge centers in the ionic liquid and the zwitterionic monomers on the main chain of the gel electrolyte jointly generate electrostatic interactions with the anions in the electrolyte, limiting the migration of the anions, thereby obtaining a higher lithium ion migration number, reducing the growth of dendrites in lithium metal batteries, and thus reducing the generation and growth of dendrites; at the same time, the negative charge centers at the ends of the zwitterionic monomers promote the dissociation of lithium salts, obtaining higher electrical conductivity, and improving the electrochemical properties of lithium ions. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A schematic diagram of preparing a high conductivity and high mobility gel electrolyte provided in the examples;

[0021] Figure 2 Schematic diagram of the principle of achieving high conductivity and high migration number of the gel electrolyte provided in the embodiment;

[0022] Figure 3 The conductivity and migration data diagram of the gel electrolyte provided in the embodiments of the present invention;

[0023] Figure 4 A cycle stability diagram of the gel electrolyte provided in an embodiment of the present invention;

[0024] Figure 5 This is a CV curve diagram of the gel electrolyte provided in an embodiment of the present invention at a scan rate of 0.5 mV / s. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0027] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.

[0028] The present invention provides a high-conductivity and high-mobility lithium metal battery gel electrolyte, which comprises a gel and a lithium salt dissolved in the gel; wherein the gel is prepared by a polymerizable ionic liquid and a polymerizable zwitterionic monomer in a molar ratio of 1:(0.5-2) under the action of an initiator, a crosslinking agent and an organic solvent to undergo a polymerization reaction.

[0029] As a specific example, the ionic liquid in the present invention is selected from but not limited to 1-allyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-allyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-allyl-3-ethylimidazolium bis(trifluoromethanesulfonyl)imide, 1-allyl-3-butylimidazolium hexafluorophosphate, 1-allyl-3-butylimidazolium bis(trifluoromethanesulfonyl)imide, 1-allyl-3-methylimidazolium tetrafluoroborate, 1-vinyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide The zwitterionic monomer is selected from but not limited to at least one of [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide, 2-methacryloyloxyethylphosphocholine, and 1-propylsulfonic acid-3-vinyl imidazole inner salt.

[0030] Example 1

[0031] In a 50 mL mixed solution of dimethyl carbonate and ethylene carbonate (volume ratio of 1:1), 20.16 g of 1-allyl-3-methylimidazole bis(trifluoromethanesulfonyl)imide salt and 13.97 g of [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide were added; then, 14.35 g of lithium bis(trifluoromethanesulfonyl imide), 0.68 g of azobisisobutyronitrile and 0.68 g of polyethylene glycol diacrylate were added to the solution, and the mixture was stirred and mixed thoroughly;

[0032] 1 ml of the mixed solution was dripped onto the polypropylene diaphragm and packaged using a battery packaging machine (all experimental operations were carried out in a glove box with a water content of less than 0.1 ppm and an oxygen content of less than 0.1 ppm); finally, the packaged battery was placed in an oven at 60°C for 12 hours.

[0033] like Figure 2 As shown, the positive charge center of the zwitterion and the ionic liquid in the present invention jointly restricts TFSI - ions, thereby enabling the electrolyte to obtain a higher lithium ion migration number; and the negatively charged groups of the zwitterions can also promote the dissociation of lithium salts and the movement of lithium, thereby obtaining a higher lithium ion conductivity.

[0034] In the present invention, referring to the method provided, PDAS (pure zwitterionic monomer), the molar ratio of zwitterionic monomer to ionic liquid is 1:2 (25%), 1:1 (50%), 2:1 (75%), and PBT (pure ionic liquid) are used to prepare the gel electrolyte. Figure 3As shown, when the ratio of zwitterions to pure ionic liquid is 1:1, the electrolyte obtains the largest migration number, which indicates that the combination of the two has the best effect on anion migration and also enables the electrolyte to obtain a higher conductivity.

[0035] like Figure 4 As shown in Figure 2, when the ratio of zwitterion to ionic liquid is 1:1, the gel electrolyte maintains cycle stability at a current density of 0.1C for 80 cycles with a capacity of 145 mAh g -1 .

[0036] like Figure 5 As shown in the figure, when the ratio of zwitterion to ionic liquid is 1:1, the gel electrolyte has an oxidation peak and a reduction peak. And the peak currents are basically the same, indicating that the gel electrolyte has good reversibility.

[0037] The above are only preferred embodiments of the present invention, and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the description and illustrations of the present invention should be included in the protection scope of the present invention.

Claims

1. A high conductivity and high mobility lithium metal battery gel electrolyte, characterized in that: The gel electrolyte includes a gel and a lithium salt dissolved in the gel; The gel is prepared by polymerization reaction of a polymerizable ionic liquid, a polymerizable zwitterionic monomer, an initiator and a cross-linking agent in an organic solvent.

2. The high conductivity and high mobility lithium metal battery gel electrolyte according to claim 1, characterized in that: The molar ratio of the ionic liquid to the zwitterionic monomer is 1:(0.5-2).

3. The high conductivity and high mobility lithium metal battery gel electrolyte according to claim 1 or 2, characterized in that: The ionic liquid is one or more of 1-allyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-allyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-allyl-3-ethylimidazolium bis(trifluoromethanesulfonyl)imide, 1-allyl-3-butylimidazolium hexafluorophosphate, 1-allyl-3-butylimidazolium bis(trifluoromethanesulfonyl)imide, 1-allyl-3-methylimidazolium tetrafluoroborate, 1-vinyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-vinyl-3-methylimidazolium hexafluorophosphate, 1-vinyl-3-ethylimidazolium bis(trifluoromethanesulfonyl)imide, 1-vinyl-3-ethylimidazolium hexafluorophosphate, and 1-vinyl-3-ethylimidazolium tetrafluoroborate.

4. The high conductivity and high mobility lithium metal battery gel electrolyte according to claim 1 or 2, characterized in that: The zwitterionic monomer is one or more of [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide, 2-methacryloyloxyethyl phosphorylcholine, and 1-propylsulfonic acid-3-vinyl imidazole inner salt.

5. The high conductivity and high mobility lithium metal battery gel electrolyte according to claim 1 or 2, characterized in that: The lithium salt is one or more of lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl imide), lithium perchlorate, and lithium tetrafluoroborate.

6. The high conductivity and high mobility lithium metal battery gel electrolyte according to claim 1 or 2, characterized in that: The initiator is one of an azo initiator or a peroxide initiator.

7. The high conductivity and high mobility lithium metal battery gel electrolyte according to claim 1 or 2, characterized in that: The organic solvent is one or more of dimethyl carbonate, ethylene carbonate, propylene carbonate, diethyl carbonate, tetrahydrofuran, 1,3-dioxolane, diethyl carbonate / ethylene carbonate, ethylene glycol dimethyl ether / 1,3-dioxolane, and ionic liquid.

8. A method for preparing a high conductivity and high migration number lithium metal battery gel electrolyte, characterized in that: The method for preparing a high-conductivity and high-mobility lithium metal battery gel electrolyte according to any one of claims 1 to 7 comprises: Adding a polymerizable ionic liquid, a polymerizable zwitterionic monomer, a lithium salt, an initiator, and a crosslinking agent into an organic solvent, and stirring and mixing the mixture to form a mixed solution; The mixed solution is dripped onto the separator, and the solution is encapsulated and thermally polymerized to form a high-conductivity and high-migration number lithium metal battery gel electrolyte.

9. The preparation method according to claim 8, characterized in that: The diaphragm is a polypropylene diaphragm.

10. A lithium battery, characterized in that: The electrolyte in the lithium battery is the high-conductivity and high-mobility number lithium metal battery gel electrolyte as described in any one of claims 1 to 7.

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